Power transistors for controlling power have been widely used in industrial devices including computers. Since power transistors supply power, they generate a large amount of heat. Generally, a fuse is connected to a base or gate of a power transistor in order to protect the power transistor.
The fuse breaks when the temperature thereof reaches a predetermined dangerous temperature, thereby turning-off and cooling the transistor so as to protect it. An inexpensive fuse is used in expensive equipment so that a system including the equipment can be protected by checking whether the fuse is cut. However, a problem occurs when changing/replacing the fuse.
When changing/replacing the fuse, although the fuse is inexpensive, it take a certain amount of time and costs are incurred when hanging/replacing the fuse, and economic loss may be caused since equipment cannot be used during changing/replacing the fuse. Accordingly, research has been conducted on a device that can function as a fuse and can be continually used without needing to be changed/replaced and on a method and circuit for controlling radiant heat of transistor using the device.
Currently, when a secondary cell is charged, a power transistor through which a current of at least 500 mA can flow is required. In this case, a temperature of the power transistor (TIP 29C and a maximum current of 2 A) can be increased to a temperature equal to or greater than 100° C., for example, 140° C. Thus, a temperature fuse is used to protect a power system, and an aluminum heat sink is used to cool heat generation by the power system.
Power transistors use an aluminum heat sink to prevent heat generation. In this regard, since the size of a heat sink is greater than that of a transistor, the heat sink occupies a large space in a power system, which is an obstacle to miniaturization of such power systems. In addition, since radiant heat of a transistor is waste thermal energy converted from electrical energy, problems regarding radiant heat should be overcome to improve energy efficiency.